Ram air turbines have been utilized in a variety of aeronautical applications. Not untypically, they are utilized as auxiliary power sources. For example, ram air turbines may be connected to electrical generators which serve as an auxiliary electrical generator. When the main power generators experience difficulty in operation, the ram air turbine is deployed in the air stream in which the aeronatical vehicle is travelling. The force of the passing ram air on the turbine will cause the same to rotate and provide mechanical motion necessary to drive the generator.
Ram air turbines have also been utilized in connection with air-to-air refueling apparatus. In such a case, they may be utilized to drive a pump which in turn transfers fuel from one aircraft to another during a refueling process.
Particularly when ram air turbines are utilized as part of refueling apparatus, they are unlikely to be stowed out of the air stream until their use is required. As a consequence, it is desirable that they provide minimal drag on the aircraft on which they are mounted while the same moves to and from a refueling point. This will generally dictate that variable pitch blades used as part of the ram air turbine be maintained in a feathered position except when operation is intended.
It is also desirable that the turbine be locked against rotation except when in use. This is particularly desirable when the aircraft carrying the apparatus is located on an air field or a carrier deck. If surface winds were permitted to cause windmilling of the turbine, bodily harm could come to maintenance personnel in the vicinity of the apparatus.
It is also desirable that the ram air turbine include means whereby the same will revert to a feathered configuration in the event of a failure within the system. And of course, it is most desirable of all that these features be provided by a simple and reliable system.